Ubuntu with 1 app
It's pretty clear that "ChromeOS" is just going to be Ubuntu with Chrome installed (see omgubuntu.co.uk for info and screenshots)... Chrome then has the clock, battery and wifi integrated into it's title bar.
Hardly any of the 'general population' has heard of Ubuntu, but EVERYONE has heard of google - and I reckon it won't take long for a chunk of PC users to start demanding "the simplicity of google chrome" (ie. no viruses or apps, just pure web browsing). They can't complain at the price either.
It could be the start of a mass migration to Linux in all but name. What bets M$ will start offering Windows for £0 to consumers soon?